mapping to ICD9 or ICD10 based on admit_date

[dckc]

In #43 I see a familiar issue:

The ICD10 ontology intentionally includes ICD9 c_basecodes so that users can query an ICD10 code and also get the equivalent ICD9 code.

FWIW, I just wrote code to handle this by mapping to ICD9 before a certain cut-off and ICD10 after. It's somewhat specific to KUMC, but in case it helps: https://github.com/kumc-bmi/i2p-transform/blob/d15d7cc46070700299cd3c4a37d4e5455240898d/Oracle/PCORNetLoader_ora.sql#L1012-L1039

p.s. lumping 3 issues into #43 adds friction for collaborators such as myself. Please avoid that.

cc @matthewjoss @jklann